Rep Power: 0

I recently replaced the O2 sensors, spark plugs (plus coil, rotor, etc.) on my 99 LX Civic and my average MPG has jumped from the low 30s (31 - 35) to the high 30s (37 - 43). I already had 2 tanks in the low 40s this month alone and my worst tank in recent memory is 36 MPG!

Granted, my commute is 40 miles one way and about 80% highway (in light to moderate traffic.) I've had this car for 15 years (got it new as a gift) and coudl count on a single hand the # of times I've gotten over 40 MPG on a single tank, (mostly in the car's earlier years..) and now it's doing it regularly despite over 180K miles on the odometer.

 
Rep Power: 188

Not with automatic transmission, darn torque converter. I can maybe do 37MPG all highway 65MPH or below with my auto '99 dx.

I'm sure you're not the only 1 who gets 40 with a manual 6th gen.


It's strange I think I've heard it go both ways, mileage can go higher or lower after changing o2 sensors. Depends on whether engine is running too lean or too rich before.

 
Rep Power: 203

I regularly get 40+ mpg on my stock 1999 DX 5 speed D16Y7

 
Rep Power: 0

I commute about 60 miles each way to work at the moment and was getting in the low to mid 40's on a regular basis. 2000 LX manual! cant beat it!